STRONTIUM IN MAN AND BEAST 



till" material has to go through a cell or a incmbrane there is the capacity to dis- 

 criminate across that barrier, but if the material goes through holes then presumably 

 there is less or no means ofdisi rimiiiation. It may therefore be that this will be a tool 

 for discriminating between nielhuds of jjassage across the placenta if the data are 

 confirmed. As far as investigations into abnormal calcium states are concerned, I 

 think this, at the moment, is probably purely the exercise of a few people in clinical 

 research departments, who are interested in hone pathology and abnormal bone 

 physiology. There is no set programme thai I know of It depends on the interest 

 of the individual, and at present with the free availability of radio-active calcium, 

 many of these states are being investigated with radio-active calcium. The high 

 specific activity material which one would require for clinical investigation is still 

 extremely expensive. 



Parathormone of course, has been used for the decontamination of subjects 

 contaminated both with strontium and earlier with radium, but it is not a particularly 

 effective agent because it takes a very long time to act and to produce any substantial 

 elimination of calcium and the contaminate. However, you saw from the calculated 

 graph, and it can be shown directly with radio-active isotopes, that the uptake into 

 bone from plasma and extracellular fluid is extraordinarily rapid. There is no method 

 of blocking this very rapid uptake that we know of. This is to be desired from the 

 point of view of treatment of accidental contamination, that is, some method which 

 would block only the uptake as and when required. But again, presumably this is a 

 physico-chemical problem, the earliest uptake of calcium and strontium ions by the 

 bone being, probably, a physico-chemical process and one would have to defeat this 

 process. 



Mr. Jackson: I should like to ask Dr. Loutit if milk teeth in children have been used 

 as an index, not merely of strontium but of deficiencies in calcium phosphate meta- 

 bolism. Could children with the various known deficiencies be taken and their milk 

 teeth examined as a method of estimation ? 



Dr. Loutit: Well, I am sure that those who are interested in calcium metabolism 

 and dental problems in general can answer part of your question, but I am not well 

 versed in dental physiology. As far as the problem of monitoring is concerned — is 

 the milk tooth an indicator in vivo, of the degree of contamination of the subject? 

 The answer is, in theory — yes; the calcium and strontium will be laid down in the 

 milk tooth during a well-defined period of time. The amount of ®°Sr in the milk 

 tooth is, therefore, an indicator of the contamination in the extra cellular fluid of 

 the foetus, or the newborn during that time. However, the mass of a milk tooth is so 

 small that the concentration of '"Sr at the present levels could not be physically 

 determined in a milk tooth. It would be practicable, of course, to collect the central 

 upper right incisors of all children born in certain months and to bulk them. This 

 would give only a broad figure, and as you saw there is considerable individual 

 variation in a population such as the British population. So it is practicable but, for 

 use on a mass basis, it would be very difficult administratively. 



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